Radiofrequency (RF) therapy, is a well known non-invasive and outpatient procedure that uses radio waves. Generally, it is used to treat cancer, more particularly for the ablation of tumors from different organs, e.g. breast, colon, lungs, pancreas, prostate, kidney.
In such procedure, electrodes are placed into contact with the tissue to treat and a current, from a RF generator, is applied to the tissue via the electrodes. As the current passes, the tissue between the electrodes heats, a lesion is created, and the corresponding tissue is destroyed.
RF surgical devices are well known. Generally they are monopolar devices.
The device described in U.S. Pat. No. 5,507,743 may be a monopolar or a bipolar device. In the bipolar form of the device, it comprises one straight and one helical (coiled) electrode, the straight electrode being inside the helix formed by the helical one. In U.S. Pat. No. 5,507,743, to increase the size of the lesion created, both electrodes are hollow with a plurality of fluid distribution ports to deliver, into or onto the tissue to be ablated, a conductive fluid, such as chemotherapeutic agent or as an isotonic or hypertonic saline solution.
One of the main disadvantages of such RF surgical devices is that no confinement of the lesion is achieved. Furthermore it is very difficult to predict how wide the lesion created will be.
In WO2004/100812, the bipolar RF device is a three elements device wherein at least two of the elements are “dry” electrodes, i.e. not hollow and not able to deliver a conductive fluid. In the bipolar RF device described, the electrodes may be either both helical (coiled) and parallel one to another, or one helical and one straight. The bipolar RF device works by a cage effect allowing some confinement of the lesion created.
One of the main disadvantages of such bipolar RF surgical devices working with a cage effect, is the imprecise confinement of the lesion created as the positioning of the RF electrodes, to effectively ablate the tissue, may be imprecise.
To ensure optimal performance, the axis of each electrode should be parallel; However, due to the piercing resistance of the skin, the tissue, or the organ to treat, and even if Radiofrequency electrodes are sharp and not deformable, the electrodes are prone to touch, or come close, one to another, leading to a misalignment of the electrodes and a reduced performance of RF devices.
In addition, a controlled widening of the confinement is not possible with such bipolar RF surgical devices.